Validation of the "L-DOPA test" for diagnosis of restless legs syndrome

Abstract

We developed and validated a standardized test procedure to evaluate the accuracy of the supportive diagnostic criterion "response to dopaminergic treatment" in restless legs syndrome (RLS). Forty-eight patients who fulfilled at least three of the four essential criteria for RLS, thus including uncertain clinical cases for a nonexpert, were recruited. Patients received a preliminary diagnosis of RLS or non-RLS. All patients underwent a polysomnography (PSG) and were then asked to perform the diagnostic L-DOPA test at home, which consisted in the application of one single dose of 100/25 mg L-DOPA/benserazide and a subsequent observational period of 2 hours. Before, and in 15-minute intervals after, drug intake, the patients rated the severity of the "symptoms in the legs" and the "urge to move the legs" using a 100-mm visual analogue scale. Considering a 50% improvement as a positive test result, we found a sensitivity of 88% ("symptoms in the legs") and 80% ("urge to move the legs") with a specificity of 100% for both test items. A rate of 90% or 83% of all patients could be correctly diagnosed by the L-DOPA test. Both scales were able to predict the response to dopaminergic agents in the subsequent course of the treatment by 100%. The periodic leg movements arousal index as assessed by polysomnography was less appropriate for the prediction of the correct diagnosis. We recommend the L-DOPA test for diagnostic decision making in all patients with an unclear RLS diagnosis according to the essential diagnostic criteria of the International RLS Study Group.